The effect of nitrification inhibitors on the aerobic biodegradation of tetracycline antibiotics in swine wastewater

The aerobic biotreatment process for the dual goals of antibiotic removal and ammonia retainment for the fieldreturn-based treatment of swine wastewater was optimized by adding 2-chloro-6-trichloromethylpyridine (TCMP), commonly used as a nitrogen fertilizer synergist. The results show that the dosage of 5-10 mg/L TCMP daily effectively inhibited nitrification. The COD and tetracycline antibiotics (TCs) in the absence of TCMP was removed by 91% and 76%, and became 87% and 78% with 5 mg/L TCMP and 83% and 70% with 10 mg/L TCMP, respectively. The removal efficiency of four TCs generally followed a decreasing trend of chlortetracycline (CTC) > doxycycline (DC) > tetracycline (TC) > oxytetracycline (OTC). A dosage of 5 mg/L TCMP daily inhibited ammonia nitrification effectively and only slightly affected the removal of conventional organic pollutants and TCs. The contribution of volatilization and hydrolysis to the removal of TCs was negligible. The overall removal efficiency of four TCs in removal pathway experiments was 98%, 94%, 97%, and 96% for OTC, CTC, DC, and TC, of which 69%, 41%, 56%, and 62% was contributed by absorption, and 29%, 53%, 41%, and 34% was contributed by biodegradation, respectively. This study may have significant implications for the proper man-agement of livestock wastewater intended to be used as fertilizers, which aims to reduce the exposure risk of antibiotics and preserve its nutrient value.

Automated summary

The aerobic biotreatment process for swine wastewater treatment was optimized using 2-chloro-6-trichloromethylpyridine (TCMP) as a nitrogen fertilizer synergist, to simultaneously achieve antibiotic removal and ammonia retainment. The results showed that a daily dosage of 5-10 mg/L TCMP effectively inhibited nitrification and had varying effects on the removal of COD and tetracycline antibiotics (TCs). The study also found that TCMP had minimal impact on volatilization and hydrolysis, and the overall removal efficiency of TCs was mainly contributed by absorption and biodegradation.